Wave length modulation



Oct. 30; 1945.-

. G. L. USSELMAN WAVE LENGTH MODULATION File dSept. 29, 1942 3 Sheets-Sheet l OUTPUT 'OUTPUT SIGNAL SOURCE SOURCE INVENTOR GE)ORG L. USSELMAN f ATTORNEY Oct. 30, 1945.

G. USSELMAN WAVE LENGTH MODULATION Filed Sept. 29, 1942 3 Sheets-Sheet 2 Fig.5.

SlGNAL I SOURCE OUTPUT souRcg INVENTOR GEORG USVSELMAN W ATTORNEY Oct. 30, 1945. G. L.-'USSE LMAN 3 T WAVE LENGTH MQDULATI ON Filed Sept. 29, 1942 5 sheets-sheet 5 Wu. NE:

SIGNAL SOURCE A is ..L 42 5- +D.C SlGN AL A SOURCE .INVENTOR GEORGE -USSELMAN s ATTORNEY generating system.

ietented b t. 30.

. wave LENGTH! MODULATION George L. Usoelman, Port Jeflerson, N. Y., assignor to Radio Corporation tion of Delaware of America, a corpora- Application September 29, siasenei No. 460,043 12 Claims. (01. Iva-111.5)

In this appIication I disclose a new and improved wavelength modulation system. The general object of my invention is the improvement of wave length modulation systems. In my simplified system by the use of two tubes only, I

generate timing or wavelength modulated oscil- .lations ofcarrier wave frequency in accordance with. signals.

- ,In describing my invention in detail reference will be made to the attached drawings, wherein Figures 1 to 6 inclusive each illustrates a diifercut modification of my timing modulated wave In Figure 1, C2- --L2 is a tuned tank circuit resonant substantially at the frequency of the wave generated in the absence of timing or wave length modulation thereof. a point on this tank circuit is coupled by coupling condenser C3 to the control grid electrodes GI and GI' =of a pair of electron discharge devices VI and V2 the cath odes of which are connected to ground. Coupling condensers, the function of which is known and 7 .need not be described, are included between C3 and the grids. The anodes A and A of these tubes are coupled respectively by inductance L and capacity C to a second point on the tank circuit C2L2. 'The inductance L .is aphase retarding inductance, while the condenser C is a phase advance condenser. A point on the inductance L2 is connected to the positive terminal of a source of direct current, the negative terminal current source is shunted by bypassing condensers as is the source III. I

During operation the tank circuit LC-C2 is tuned to the desired carrier; that is, the carrier applicant wishes to send out in the absence of modulation. The control grids GI and GI of tubes Vi and V2 receive excitation energy from a point on the tank circuit at one side of the point Ii grounded for radio-frequency potentials. This energy is amplified by tubes VI and V2 and delivered to the tank circuit through phaseshifting elementsL and C. a

Note that this energy is delivered back'into the tank circuit at a point on the. other side of the point I). The energy reaching the tank circuit fromtiibe Vi is retarded in phase by inductance L, while that fed to the tank circuit fromV2 is advanced in phase by the condenser C'. When no modulation is present, the amplified energies'delivered to the tank circuit by tubes VI and v: are substantially. equaLfalthough they have a fixed phase difference and their resultant takes up an intermediate phase posi- I tion which is also substantially ilxed. Since the phases of the voltages on the grids and anodes of-thetubes are substantially opposed (disregardof which is grounded as is the cathodes of tubes VI and V2.to complete the direct current circuit.

The choke LI provides a direct current path in shunt to the condenser C; The direct current source is shunted by a radio frequency bypass and coupling condenser C4,- which completes the alternating current circuit for the tubes. Note that the grids and anodes of .tubes VI and V2 I are connected to points on the tank circuit at opposite sides of the point 0 thereon grounded by condenser Ciso that at the points to which the grids and anodes are coupled voltages of opposed orsubstantialiy opposed phase appear.

The control grids GI and GI are connected by resistors RI and R2 to the opposite terminals of the secondary winding of a transformer T,

the'primary winding of which is connected to ,a source A representing signals of any nature. Bias for the control grids GI and GI is suppli'ed by a source In connected between a point' on ,the secondary winding of transformer 'I' and ground. The screen grid electrodes G2 and G2 are supplied from any sourc of direct current by leads connected as shown, and the said direct ing the phase advance caused by C and retard caused by L). we have the conditions required for the generation of oscillations in each tube.

when signal modulation is applied from A through transformer T, the energy delivered by tubes VI, and V2 respectively is alternately increased and decreased in amplitude. Since these energies havea phase difierence determined by L and C and since they are differentially modulated, the resultant of the energies delivered to the tank circuit willbe modulated in phase in accordance with signals. Now since the tubes VI and V2 are oscillators, these phase changes are added to each oscillation cycle. energies fed back to the tank are shifted in accordance with signals, the excitation voltage fed from the other end'of the tank to the grids GI and GI take on correspondingbut opposite phase changes-and produce further phase angle change. This produces a further phase change in the resultant of th energies fed back to the tank C2- -L2 to cause on 'the grids GI and GI an additional phase angle change thereby producing frequency modulation of the oscillations.

The tank circuit cz-m stiffness limits the frequency swinghaving a rapid change in phase angle with changes in frequency which resist' change in phase anglebeyond an ascertainable limit and thereby prevent the frequency or wave Since the arrangement of Figure 1.

length modulation from building up to exceed an ascertainable limit. The initial phase displacement is, of course, adjustable by. the dimensions of- L and C. a

The timing or wave length modulated oscillations may be fed from the tank circuit L2C2 Here as in the prior figures the grids and anodes of tubesVI and V2 are connectedtopoints on the tank circuitat opposite sides of the point thereon to any utilization circuits by usual coupling 1 means, such as, aninductance L4 coupled to L2. The modification of Figure 2 is in principle the same as the modification .in Figure 1, and in Figgrounded by'condense'r C4 so that at these points voltages of opposed or substantially opposed po tential appear. In other rsepects this arrangement is similar to the arrangements of the prior ures'l and 2 similar parts have been designated by similar reference characters in so far as possible.

The modification in Figure 2 differs from'that in Figure l in the following main respects An artificial-line C5--L5 is used to produce the phase displacement between the amplified ener: I gies fed by the respective tubes VI and V2 to the.

tank circuit L2C2. matching resistance R to prevent reflection of wave energy along the line. One of the tubes V2 in the modification shown has its anode A tapped on the line at a point a' frac'tion of a wave length (or a multiple of a fraction) .nearer to the tank circuit L2C2 than the point to which the anode A of tube VI is tapped. This causes the amplified energy delivered to the tank circuit from tube VI to lag in phase behind the energy delivered to the tank .circuit by the tube V2. The spacing between the points of connection of the anodes A and A to the inductance L5 of the line can be substantially anything except multiples of 1/2. However, multiples of 1/4 are believed to operate best under most circumstances.

In Figure 2 the modulation is applied differentially to the screen grids G2 and G2 of the tubes rather than-control-'grids GI and GI. Modulation does not materially affect the terminating impedance R of the line. The resistance R matches the line and prevents reflection therealong, thus assuring that both tubes are subjected to the same radio frequency voltage but'ofdifierent phase. r

The arrangement of Figure 3 also is in principle the same as the arrangements in Figures 1 and 2,

and in Figure 3 reference characters 'similar to those used in Figures 1 and 2 are made use of in so far as possible. lation is used as in Figure 2. I

The transmission line, however, has been replaced by two transmission lines L6 and L8 of This line is terminated by a In Figure 3screen grid modudiiferent lengths. In this modification the anode A of tube VI is connected to the tank circuit through the longer line and the anode A of tube V2 is connected to the tank circuit through the shorter lineLB. Consequently, the amplified energy fed from tube VI will be later in phase, that is, retarded in phase with respect to the energy fbd by the tube V2- to the tank circuit. This phase difference is determined by the line length difference A-r. As in Figure 1, any fractionor a multiple of a fraction of difierence may be used but a difference of 7/4, or a multiple thereof is preferable.

In Figure 4 I have shown a modification of the In this arrangement the phase delay reactance L and. phase advancing capacity C are located inthe grid excitation circuits of the tubes VI and V2., The grid direct current circuits include chokes L3, the ends of which remote from the grids GI and GI are connected to the cathodes. This bias circuit for the grids includes source III and a bias resistance R. The inductances L3 also serve to feed the modulation potential to the grids 'GI and GI During operation the tank circuit .L2-'C2 is tuned to the desired carrier; thatis, the carrier applicant wishes to send out in the absence of modulation. The control grids Gland G2 of tubes VI and V2 -receive"excitation energy from a point on the tank circuit at one side of thepoint 6 grounded for radio-frequency. The excitation energy is advanced in phase by thephase shifting circuit including C2, the. impedance in tube V2 between the grid and cathode, the impedance L3,

R, etc. The excitation energy fed to the grid GI and tube VI is retarded in phase bythe shifting circuit including inductance L, the

to cathode impedance of V2, L3 and-R;

, The amplified energy reaching the tank circuit from tube VI is retarded in phase by the phase; 1 retarding circuit including inductance -L, while that fed to the tank circuit from V2 is advanced 1 in phase by the phase advancing circuit including condenser C. When no modulation is present, the amplified energies delivered tothe tankcircuit by tubes VI and V2 are substantially equal,

although they have a fixed phase difference.

However, when signal modulation is applied from A through transformer T, the energy delivered by I tubes VI and V2 respectively is alternately inv v creased and decreased in amplitude.

energies have a phase difference determined-by L and C and since they are diiferently modulated. the resultant of the energies delivered to the tank circuit will be modulated in phase in accordance with signals, the operation being in general as outlined above.

The modification of Figure 5 is in principle the same as the modification in Figure i, andin all the figures similar parts have been designated by similar referencecharacters in so far as possible. The modification-in Figure 5 differs from that in Figure 4 in the following main respects:

An artificial line C5-L5 is used to produce'the phase displacement between. the excitation energies fed to the respective grids GI and GI andi tubes VI and V2 to the tank circuit L2C2.

lineis terminated by a'matching resistance R to prevent reflection of wave energy along the line.

One of the tubes VI in the modification shown has of line L can be substantially anything. except multiples of 'r/4. However, multiples of 7/4 are.

,i believed to operate best under mostv c1rcumstances.

In Figure 5, as in Figure 2, the modulation is applied differentially to the screen grids G2 of the tubes rather than control grids GI.

The arrangement of Figure 6 also is'in principle the same as the prior arrangements.

The transmission line ofFigure 5, however, has

Since these been replaced-'by-two transmission lines L6 and LI difierent lengths. In this modification the gridGl of tube Vi isconnected to the tank circuit through a line L longer than the line L8 conis determined by the line length diiference A'n' As inFlgure 1, any fraction or multiple of a fraction 01' a wave length difierence may be used but A a diflerence oi -r/4 of a multiple thereof is'preferable.

The surge impedance of lines L6 and L8 of Figure 6 is matched by resistors RI and RI which here also serve to bias the control grids GI and Gl-f. Here, as in Figure 5, the grid connection excitation leads should be made equal in length or their difierence in length made up in the transmission line lengths and connection.

What is claimed is:

1. Ina. wavelength modulation system, a tank circuit, a pair of electron discharge devices each having input and output electrodes including a cathode, a coupling between a point intermediate the terminals of the tank circuit and the cathod'es of said devices, couplings between a point on said tank circuit at one side of said intermediate point and the input electrodes of each of said devices,

couplings between a point on said tank circuit at the other side of said intermediate point and the output electrodespf said devices, whereby oscillations are generated in said devices and circuits when operatingpotentials are applied to the electrodesxot the devices' and the-generated volt- 7 ages are substantially of opposed phase on said input andoutput electrodes, phase shifters mat least one of the couplings'between the, tank circuit and an electrode of one 01 said devices to alter the said substantially opposed relation between the voltages on the input and output electrodes of said one of said devices and connections for differentially modulating the impedances of said devices in accordance with signals.

2. In a .wave length modulation system, a tank circuit, a pair of electron discharge devices each having input and output electrodes including an anode, a control grid anda, cathode, a couplingbetween a point intermediate the terminals of the tank circuit and the cathodes of said devices, couplingsbetween a point on said tank circuit at one side of said intermediate point and the control grids of said devices, phase displacing reactances of difl'erent electrical character coupling the anode of each of said devices to a point on said tank circuit on the other side of said intermediate point, connections for applying operating potenmodulating potentials and connections for applycircuit, a pair of electron'discharge devices each having input and output electrodes including a cathode, a coupling between a point intermediate the terminals of the tank circuit and the oathodes of said devices, couplings between a point on said tank circuit at one side of said intermediate point and the input electrodes of each of said devices, couplings between a point on said tank circuit at the other side oi. said intermediate -point and the outputelectrodes'oisaid devices, a separate phase-shifter in one of the couplings betweenthe tank circuit and an electrode of each device, connections ior applying operating potentials to the electrodes of said devices and connections for diilerentiallymodulating the impedance of said devices in accordance with signals.

5. ma wave length modulation system, a'tanl-r circuit, a pair of electron discharge devices each having input and output electrodes including a cathode, a coupling between a point intermediate the terminals of the tank circuit and the,

cathodes of said devices, couplings between a point on said tank circuit at one side of said interme-' diate point and the input electrodes oi' each of said devices, couplings between a point on said tank circuit and the output electrodes'of said devices, an artificial line which provides phase 1 shifting reactance in the couplings between the tank circuit and an electrode of each device, connections" for. applying operating potentials to the electrodes of said devices and connections, for

' diflerentially modulating the ,impedances 01' said devices in accordance with signals.

6. In a wave length modulation system, a tank circuit, a pair of electron discharge devices each having input and'output electrodes including ,a cathode, a coupling between a point intermediate the terminals 01' the tank circuit and the oath.-

odes of said devices, couplings between a point.

on said tankcircuit at one side of said intermediate point and the input electrodes of each of said devices, couplings between a point on said ing said modulating potentials in phase displaced relation to corresponding electrodes of said devices. N i

3. m a wave length modulation system. a tank circuit, a pair of electron discharge devices each having input and output electrodes including an anode, a control grid and a cathode, a coupling between a point intermediate the terminals of the tank circuit and the cathodes of. said devices,

couplings between. apoint on said tank circuit at one side or said intermediate pointand the anodes of said devices, phase displacing reactances oi diil'erent electrical character coupling the grid oi each oi. said devices to a point on said 1 tank circuit on the other side of said intermeditank' circuit and the output electrodes 01' said. devices, separate transmission lines of different length in a coupling between the tank circuit and an electrodeof each device, connections for apcordance with signals.

'1, In a wave length modulation system, a tank circuit, a pair of electron discharge devices each having an anode, a control grid and a cathode, a coupling between a point intermediate the terminals of the tank circuit and the cathodes of said devices, couplings between a point-on said tank circuit at one side of said intermediate point and the control grids of said devicesya phase displacing reactance coupling the anode of one of said devicesto a point on said tank circuit on the other'side oi! said intermediate point, a second phase displacing reactance coupling the anode or. the other device to said last point on said tank circuit, connections for applying operating potentials to the electrodes of said devices, a source of tentials to the electrodes of said devices, a source of modulating potentials and connections for an- 4' l 2,888,098 relation and corresponding electrodes of said 'de-;

cuiton the other side of said intermediate point,

connections forapplying operating potentials to the electrodes of said devices, a source of modulating potentials and connections for applying said modulating potentials in phase displaced re- 7 lation to corresponding electrodes of said devices.

9. In a wave length modulation system, a tank circuit, a pair of electron discharge devices each having an anode, a control grid and a cathode, a coupling between a point intermediate-the terminals of the tank circuit and the cathodes of said devices, couplings between a point on said tank circuit at one side of said intermediate point "placing line coupling the anode of one of said devices to a point on'said tank circuit-on the other side 01. said intermediate point, a second Phase displacing line of less length coupling the anode of the other'device to said last point on said tank circuit, connections for applying operating potentials to the electrodes of said devices, a source r of modulating potentials and connections for applying said modulating potentials in phase displaced relation and.corresponding'electrodes of said devices. a

10. In a wave length modulation system, a tank circuit, a pair of electron discharge devices each having an anode, aacontrol grid and a cathode, a coupling between a point intermediate the termi nals of the tank circuit and the cathodes of said 'devices, couplings between a point-on said .tank circuit at one side of said intermediate point and the, control-grids of each of said devices, couplings between a point on said tank circuit and the anodes or said devices, an artificial line which provides phase shitting reactance in the couplings betweenthe tank circuit and the anode of each device, connections roe: applying operating potentials to the electrodes-of said devices, and connections for differentially modulating the impedances of said devices in accordance with sigl1. In a wave length modulation system, a tank circuit, a pair of electron discharge devices each 19 having an anode, a control grid and a cathode,a

coupling between a point intermediate the ter minals of the tank circuit and the cathodes oi said devices, couplings between a point on said tank circuit at one side of said intermediate point 15, and the control grid of each of said devices, couplings between a point on said tank circuit and the anodes of said devices, a phase shifting inductance in the coupling between the tank circuit and the control grid of one device, a phase .20 shifting condenser in the coupling between the tank circuitand the control grid of the other device, connections for applying operating poten-',

tials to the electrodes of said devices and connections for differentially modulating the im-v 25 pedances'of said devices in accordance with sigand the control grids of said devices, a phase dis-,

12. In awave length modulation system, a tank I circuit, a pair of electron discharge devices each;

having a control grid, an anode and a cathode, a 80 coupling between a point intermediate the terminals o! the tank circuit and the cathodes of said devices, couplings between a pointon' said tank circuit at one side or said intermediate point and the control grid of each of said devices, cou- 35 plings between a point on said tank circuit and e the anodes of each of said devices, said last named coupling comprising an artificial line with spaced points thereon coupled to the anodes of the de I vices to provide phase shiftingreactance of dif- 4 ferent electrical length in the couplings between the tank circuit and the anode of each device,

connections for applying operating potentials to the electrodes of said devices and connections for 4 5 devices in accordance with signals.

GEORGE L. UssEi AN. 

